The present invention relates to a composite magnetic body used to suppress electromagnetic Interference brought about by interference from unwanted electromagnetic waves in a high-frequency band and to an electromagnetic interference suppressing body obtained by the use thereof, and more particularly to a such a composition of a fireproof type.
Cellular phones, personal computers, and other types of electronic equipment operated at high frequencies such as quasi-microwave band have become more widespread in recent years. In particular, smaller and lighter devices are urgently needed, with electromagnetic noise/interference posing a serious problem.
In view of this, composite magnetic bodies and electromagnetic interference suppressing bodies are being commercialized as a means of countering such high-frequency electromagnetic interference.
Conventional composite magnetic bodies and electromagnetic interference suppressing bodies, obtained by the use thereof are fireproofed by use of halogen-based fire retardants or by means of antimony trioxide as a fire retardant aid. Typically, such fireproofing techniques using halogen-based fire retardants and/or antimony trioxide fire-retardant aid are ordinary methods that are also applied to coating materials for electric wires or the like; casings for electronic equipment; and other products.
In some composite magnetic bodies, chlorinated polyethylene is used as a binding agent in order to improve the fire resistance characteristics or the filling properties of soft magnetic powders, and they also contain chlorine, which is a halogen.
There is a problem indications indicated that dioxins might be released under certain incineration conditions during the incineration disposal of chlorine-contained materials, although it has not yet completely understood.
Another problem, currently difficult to prove because of the absence of reliable reports, is a possible release of dioxins by fire retardants and other halogen-containing materials.
Concern is mounting regarding environmental issues and health safety, creating a need for the development of materials that are free of halogens and do not harm the environment.
In view of this, it is an object of the present invention to provide a composite magnetic body that is completely free of halogen-containing materials, for example, halogen-containing binding agents such as halogen-based resins or elastomers, and halogen-containing bromine-based fire retardants.
It is another object of the present invention to provide an electromagnetic interference suppressing body using this composite magnetic body.
In order to attain the stated objects, the present invention is directed to fireproof of a composite magnetic material without use of a halogen-based binding agent with good powder filling properties in the material and a halogen-based fire retardant having an adequate fire resistance effect.
According to an aspect of the present invention, there is obtained a composite magnetic body comprising a silicone rubber and a soft magnetic powder dispersed in the silicone rubber.
Preferably, in the aspect of the present invention, the silicone rubber may be a solid silicone rubber or a liquid silicone rubber of a chemically-setting type.
The silicone rubber may contain an additive containing at least one selected from a group consisting of platinum, silicon, titanium, iron, copper, nickel, and cobalt
The silicone rubber may contain carbon black.
The soft magnetic powder may be a magnetic alloy powder having a flat shape.
The soft magnetic powder may have a specific surface area of 0.1-3 m2/g, have an aspect ratio of 3 or more.
The soft magnetic powder may be surface-treated with a coupling agent having a SP value ranges from 6 to 10.
The coupling agent may be at least one compound selected from titanate, aluminate, and silane.
Also, the soft magnetic powder may be surface-treated with a primer having a SP value less than that of the soft magnetic powder but greater than that of the silicone rubber.
According to another aspect of the present invention, there is obtained an electromagnetic interference suppressing body characterized in that the aforementioned composite magnetic body is used to suppress electromagnetic interference brought about by interference from unwanted electromagnetic waves.